Biophysics Core The BIOPHYSICS CORE provides specialized equipment and technical expertise for the structural characterization of macromolecules. It enables and assists all members of the Program of Projects in the analysis of complex macromolecular systems by means of Analytical Ultracentrifugation, Circular Dichroism, Fluorescence Spectroscopy and X-ray Diffraction. These techniques provide solution-state and structural information on biological macromolecules and their complexes, such as molecular weight, aggregation state, monodispersity, hydrodynamic properties (size, shape), secondary structure (folding), and interactions (binding energy, rate constants, etc), and streamlines structure determination by x-ray crystellography. In the context of this Program of Projects, these approaches will be applied to study the interaction between histone chaperones, histone acetyltransferases, and other cellular factors, to investigate the enzymatic mechanism of histone acetyl transferase, and to assay the compaction state of chromatin fibers. The Biophysics Core is co-directed by two full-time Ph.D.-level Directors with many years of experience in the use of all listed experimental approaches. The Biophysics Core has the following Specific Aims: AIM 1:To use analytical ultracentrifugation to characterize the homogeneity/ aggregation state, shape and size of relevant chromatin-associated proteins. AIM 2: To characterize the purity and stoichiometry of protein-complexes using analytical ultra-centrifugation. AIM 3: To check the integrity of mutant proteins using circular dichroism. AIM 4: To determine the thermodynamic and kinetic parameters for proteins involved in chromatin dynamics using fluorescence spectroscopy. AIM 5: To support the determination of three-dimensional macromolecular structures by means of X-ray diffraction experiments and high-resolution native and derivative date collection. AIM 6: To provide electronic raw data storage, data processing and interpretation capabilities, including computer hardware and software.